OK, I’ve been digging deeper into this rabbit hole…
As awesome as LEDs are, I’ve determined that they may not be the best solution for this project. In terms of budget, I think I can get a lot closer to the goal by using a metal halide HID lamp and an 18” parabolic reflector. I found a project over on CPF where the guy made his own 24” reflector from foam & fiberglass. It was lined with chrome tape from an auto parts store. So, not exactly the best reflector in terms of optics or efficiency. Yet he was getting the type of beam results I want with a 100-watt HID. And his 400-watt HID was what I’m looking for in terms of beam visibility. The 400-watt MH-HID lamps I’ve seen so far are rated at about 36,000 lumens. And those are brand-name lamps like Sylvania and Lithonia (and I personally know the engineer that used to head the photometric lab at Lithonia, so that’s probably an accurate rating and not “internet lumens”. 36,000 basic radiated lumens ain’t a bad start. And I can get that for about $100 shipped from 1000bulbs. (still comparison shopping though). Plus, better quality aluminum parabolic reflectors are now available for under $100 US. I found an 18” listed for around $60, which seemed to be the best deal for the money. NASA Searchlights uses 18” reflectors in their commercial rigs, so that’s probably enough for this project.
Now here’s where the fun begins. For a few dollars more (insert Clint Eastwood meme here), I could step up to a 1,000-watt MH-HID. That would put me in the $150 range for the lamp, ballast, base, and shipping. But it would get me around 110,000 base lumens! I could probably make a searchlight out of a trash can lid with that kind of power.
So, I may end up asking the MODs to move this thread over to the HID forum. But here’s what I’m thinking so far…
18” Edmund Scientific aluminum parabolic reflector
400-watt MH-HID lamp (or maybe 1kw ???)
custom-built enclosure and focal length/focusing rig
Some sort of shutter mechanism (probably made of steel to deal with the heat)
The shutter will be necessary because the effect I need is “instant on”, and that’s not possible with HIDs. The goal of the beam-effect is to punctuate the crescendo of the song that the Christmas lights will be choreographed to. When the song reaches the crescendo, what I want is BAM! INSTANT 1,000 FT TALL TOWER OF LIGHT! The effect will only need to be seen for about 10 seconds. Then it needs to be gone, because the song fades down and the lights will too.
OK, back down into the rabbit hole. Gotta explore the effect of arc length on beam width today.